1. Field of Invention
The invention relates to an image capturing apparatus and an auto-focusing method of the image capturing apparatus. More particularly, the invention relates to an image capturing apparatus applied for fundus examination and an auto-focusing method of the image capturing apparatus.
2. Background
The saying goes that human eyes are the window to the soul, and thus eye health is vital to human beings. The blood vessels may be directly seen from observing the fundus of an eye, such that the fundus examination may be performed periodically to track and inspect systematic disease, especially blood vessel lesions (e.g., diabetic retinopathy). Common ocular inspection apparatuses include pneumatonometers, refracting instruments, fundus cameras, and so on. Here, the fundus camera is an image capturing apparatus for capturing an image of the fundus of an eye, so as to facilitate diagnosis of ocular lesions.
A conventional image capturing apparatus for fundus examination is required to be able to adjust an imaging focal distance to the fundus of an eye in compliance with curvatures of different eye surfaces to be tested, and thereby the clear fundus image can be captured. For instance, according to the related art, light beams generated by two rectangular illuminating slits are refracted to an image sensor to be detected. The light beams enter a crystalline lens of an eye in parallel, and the light beams are refracted and focused on locations around the retina of the fundus. After the locations of two light points obtained by refracting the light beams back to the image sensor are calculated, the location of the focal point may be acquired for moving the lens and focusing on the retina of the fundus.
However, according to the related art, the image sensor need be aligned to the pupil manually, and the image sensor can focus on the fundus of an eye after the pupil is already aligned to the image sensor. The manual alignment of the image sensor to the pupil during the fundus examination is inconvenient and consumes significant time.